Every time when building a larger track I have trouble closing it. Do I need Q or K. Or two times Q. I thought why don't we make a B straight whit slots in more places then only at the end? This way you can always connect the last pieces. And you don't have to tape the last piece to the floor.

As the slots don't actually require any material removal it's something you could probably do yourself with a Stanley knife (or boxcutter as I believe it's called in the US and elsewhere). Making the slots a bit longer than standard might allow some extra adjustment, but too long and it won't hold well.

Use Painters Blue tape to hold overlaps down, and Schoey, Flyover SUCK! way too steep, and they can damage the steering slamming down as hard as they do. Build your own out of Foamboard and packing tape, and smooth out the transitions